A huge variety of marine microalgae are known to emit blue light when they are exposed to flow induced forces on their surface. This response is hypothesized to function as a defense strategy. Upon the sensing of mechanical forces a biochemical signaling cascade is triggered, which eventually results in light emission. However, the nature of mechanosensing is not completely understood and the difference between shear and normal force-induced bioluminescence is still puzzling. Here, we use micropipettes to hold and deform the single cellular microalgae Pyrocystis lunula. The bioluminescent response is studied using high speed and high sensitivity image acquisition. A precise control of the deformation and deformation rate of the organism enabled us to extract the complex strain dependence of the bioluminescent performance. Moreover, we investigate the dynamics of the flashes and extract the internal time scale of both signal transmission and the bioluminescent reaction itself.